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PUBLICATIONS

1998

Multimedia applications require a guaranteed level of service for accessing Continuous Media (CM) data, such as video and audio. To obtain such guarantees, the database server whom the data is…

1997

There is often a need to get quick approximate answers from large databases. This leads to a need for data reduction. There are many different approaches to this problem, some of them not…
In most database systems, the values of many important run-time parameters of the system, the data, or the query are unknown at query optimization time. Parametric query optimization attempts to…
Scheduling query execution plans is a particularly complex problem in hierarchical parallel systems, where each site consists of a collection of local time-shared (e.g., CPU(s) or disk(s)) and…
The result size of a query that involves multiple attributes from the same relation depends on these attributes' joint data distribution, i.e., the frequencies of all combinations of attribute…
For the past few years, we have been involved in an effort to develop a Desktop Experiment Management Environment that many experimental scientists would like to have on their desk. The environment…
Despite much interest in the area of Scientific Database Systems [2, 11], a major problem that many experimental scientists are still facing today is that there are no adequate experiment…
The notion of when two schemas are equivalent is fundamental to database design, schema integration, and data model translation. An important notion of schema equivalence, query equivalence was…
A database system that provides independence between the query and physical structure of the database tables by captioning each database table with a partial query reflecting the contents of that…

1996

Human-computer interaction (HCI) is the study of how people design, implement, and use interactive computer systems and how computers affect individuals, organizations, and society. This…
Dynamic queries constitute a very powerful mechanism for information visualization; some universe of data is visualized, and this visualization is modified on-the-fly as users modify the range of…
The amount of information that is generated and becomes available in today's world is alarming. Large databases used to be available only in major corporations and organizations. Now the smallest…
Many commercial database systems use some form of statistics, typically histograms, to summarize the contents of relations and permit efficient estimation of required quantities. While there has…
Over the last decade, a dramatic increase has been observed in the ability of individual experimental scientists to generate and store data, which has not been matched by an equivalent development…
The problem of translating database objects into a flat format to be written out in a flat Ascii file or, conversely, translating the contents of a file into a complex database object arises in…
Scheduling query execution plans is an important component of query optimization in parallel database systems. The problem is particularly complex in a shared-nothing execution environment, where…
Among existing tools for laying out large collections of visual objects, some perform automatic layouts, possibly following some rules prespecified by the user, e.g., graph layout tools, while…
Many commercial database systems maintain histograms to summarize the contents of relations and permit efficient estimation of query result sizes and access plan costs. Although several types of…
Several modules of a database system require estimates of (sub)query result sizes, e.g., query optimizers or sophisticated user interfaces providing such estimates as feedback to users before a…
This short report summarizes the discussions and recommendations of the working group on “Query Optimizer Benchmarks and Cost Model Verification”. It does not propose an actual benchmark, but…
Physical data independence is touted as a central feature of modern database systems. It allows users to frame queries in terms of the logical structure of the data, letting a query processor…
Given a query, there are many access plans that a database management system (DBMS) can follow to process it and produce its answer. All plans are equivalent in terms of their final output but vary…

1995

This paper examines the scheduling of concurrent requests on multimedia storage servers consisting of multiple resources, which is a central issue in processing and optimization of complex queries…
Conjuctive queries are queries over a relational database and are at the core of relational query languages such as SQL. Testing for containment (and equivalence) of such queries arises as part of…
Several recent trends have changed the usage and users of schemas beyond those of a database administrator’s tool for describing database contents. Distribution of computing power to the desk-top…
Many current database systems use some form of histograms to approximate the frequency distribution of values in the attributes of relations and based on them estimate some query result sizes and…
Many current database systems use histograms to approximate the frequency distribution of values in the attributes of relations and based on them estimate query result sizes and access plan costs.…

1994

Several types of data organizations have been proposed in the literature for object-oriented and relational databases. In studying these organizations, there appears to be no underlying common…
Physical data independence is touted as a central feature of modern database systems. Both relational and object-oriented systems, however, force users to frame their queries in terms of a logical…
Many aspects of database systems have been improved by Graphical User Interfaces (GUIs). One area that has not received adequate attention in GUI research is the visual presentation of schemas,…
When we, humans, talk to each other we have no trouble disambiguating what another person means, although our statements are almost never meticulously specified down to very last detail. We “fill…
In the spirit of interdependence of the different areas of CHI research, we present a description of OPOSSUM, a visualization tool inspired by concepts from heterogeneous databases. OPOSSUM is a…
Current theoretical work offers measures of schema equivalence based on the information capacity of schemas. This work is based on the existence of abstract functions satisfying various…
We describe the design and implementation of BERMUDA, which is a loosely coupled system interfacing Prolog to the Britton-Lee Intelligent Database Machine (IDM-500). BERMUDA allows multiple…
Current theoretical work offers measures of schema equivalence based on the information capacity of schemas. This work is based on the existence of abstract functions satisfying various…

1993

Many current relational database systems use some form of histograms to approximate the frequency distribution of values in the attributes of relations and on this basis estimate query result sizes…
Several graph-based algorithms have been proposed in the literature to compute the transitive closure of a directed graph. We develop two new algorithms (Basic_TC and Global _DFTC) and compare the…